Tools for tanning and softening hides have been discovered, along with needles, stone implements for punching leather, and bronze buttons.

To conserve heat on the cool highland plateau, houses did not have any doors, they were entered through openings in the roof.

Treasure

For the same reason, according to archaeologists, homes appear to have shared walls.

Hundreds of tiny bulls' heads, carved from stone, and thought to have ritual significance, were found around the sites.

Gold earrings, bracelets and rings, copper and bronze daggers, and multiple-necked pottery jugs were also found in one excavation, which might have been a burial chamber.

The archaeological find has got in the way of a housing project

A cultural resource specialist with the World Bank, which is funding a survey of the area, said it was essential that local people were adequately informed about their cultural heritage so that they could make their own decisions about how to manage it.

"This is a very exciting find," she said.

"We hope these early projects will provide evidence that cultural assets are very significant and that they should be preserved and enhanced for the economic growth of the country," she added.

The sites are scattered across a large area of what is considered prime development land to the south and west of the city, much of it already earmarked for new housing.

Crucial evidence

Archaeologists from the University of Asmara are hoping to complete an urgent survey of the area to assess the extent of the find before any building work commences.

The project also plans to build an open-air museum on one of the sites, to provide information to the public and display items found there.

Experts believe the sites provide crucial new evidence that people lived in populated, settled farming communities in the Horn of Africa as early as 800 BC.

"This is one of the richest heritage areas in Africa," said Professor Peter Schmidt, a specialist in African archaeology and dean of the College of Arts and Social Sciences at the University of Asmara.

"It can be compared to Athens and Rome as it has excellent parallels to those places. There is a remarkable opportunity to use this as a centrepiece of national preservation," he added.

The potential for tourism revenue from such important prehistoric sites is considerable.

Last year, many tourists visited Ethiopia's ancient monuments at Aksum.

It is likely that the sites on the outskirts of Asmara, which contain remnants likely to predate the Aksumite period (of the first to the sixth centuries AD) by many centuries, could also attract foreign and domestic tourists.

But archaeologists fear that it may be too late to save some of the sites.

They are seeking funding to erect a fence around one excavation, which has been partly destroyed by bulldozers digging stone for road building.

Another potentially important site has already been broken up by new housing.